Water Damage: Repairing Ceiling Drywall Defects at Seams?

Iím a long-term tenant in an apartment where the owner installed a new drywall ceiling as part of a larger construction job (building is from 1920ís and previously had all metal lathe/plaster ceilings & wood lathe/plaster walls).
A few months later, the steam radiator valve exploded in the apartment above and I could hear the water gushing: then I could see some of the ceiling drywall seams swelling and water started to drip down through one area? After the leak abated and dried, there are now two types of defects present in the ceiling drywall:

1) A fine crack of approximately 4í running along one of the drywall seams.
2) The seam of another drywall joint, approximately 5í long, is swollen and bulging slightly but isnít cracked.

Iím more familiar repairing plaster defects than with drywall, which is sort of new to me. After the construction I sent a lot of time restoring this room and skim coating it. Except for these new defects, the ceiling is a beautiful and spotless flat planeÖ.Iíd like to keep it that way. The ownerís workers will come in to repair the ceiling defects, but honestly these guys are monkeys who donít care about the appearance of their work (or donít know how to do it correctly). I wouldnít be surprised to see huge mounds of drywall slapped over the seams.

Question: How best to perform the repairs to these two type of drywall defects? Iíd like to provide some guidance, and if need be, intervene.

Water Damage: Repairing Ceiling Drywall Defects at Seams?

Water Damage: Repairing Ceiling Drywall Defects at Seams?

Cut out old tape and reapply new set in drywall mud. It will take at least 3 coats to get it right.
Only sand the last coat. The other tow you just drag the drywall knife across it to knock off the high spots.
Apply thin coats of compound!

Water Damage: Repairing Ceiling Drywall Defects at Seams?

Just because you do not see it does not mean the backside of the drywall was not damaged. Especially if there was that much water. Among other things it may be compromised around the fasteners if the joints are sagging. You should not just repair seams and think you have resolved the problem long term.

Refer this to your landlord. Offer to mud and tape if you do not trust his workers. I guess. The minute you touch this you take on the responsibility for whatever is wrong up there.